Editing Dynamo theory (section)

=== Practical measure of possible dynamos ===
The most functional feature of kinematic dynamo theory is that it can be used to test whether a velocity field is or is not capable of dynamo action. By experimentally applying a certain velocity field to a small magnetic field, one can observe whether the magnetic field tends to grow (or not) in response to the applied flow. If the magnetic field does grow, then the system is either capable of dynamo action or is a dynamo, but if the magnetic field does not grow, then it is simply referred to as “not a dynamo”.

An analogous method called the ''[[membrane paradigm]]'' is a way of looking at [[black hole]]s that allows for the material near their surfaces to be expressed in the language of dynamo theory.